A transcription factor TaMYB5 modulates leaf rolling in wheat.

Leaf rolling is an important agronomic trait in wheat ( L.). Moderate leaf rolling keeps leaves upright and maintains the relatively normal photosynthesis of plants under drought stress. However, the molecular mechanism of wheat leaf rolling remains unclear. Here, we identified a candidate gene that regulates leaf rolling by using a genome-wide association study (GWAS) in a panel of 323 wheat accessions. Phenotype analysis indicated that the leaves of mutants were flatter than that of the wild type under drought condition. A nucleotide variation in the coding region resulted in a substitution of Thr to Lys, which corresponds to two alleles -3A-1 and -3A-2. The leaf rolling index (LRI) of the -3A-1 genotype was significantly lower than that of the -3A-2 genotype. In addition, alleles were associated with canopy temperature (CT) in multiple environments. The CT of the -3A-1 genotype was lower than that of the -3A-2 genotype. Gene expression analysis showed that was mainly expressed in leaves and down-regulated by PEG and ABA treatment. TaMYB5 induces gene expression through the direct binding to the AC -acting element of the promoter of the target gene, which was validated by EMSA (electrophoretic mobility shift assay). Our results revealed a crucial molecular mechanism in wheat leaf rolling and provided the theoretical basis and a gene resource for crop breeding.